francisco in 72 foot boats with the hard wing. the ac 45s that we're sailing in the world series are a smaller version of the boats racing in the america's cup. >> what are the differences of the size and speed? >> well, actually, the ac 72s are, you know, a fair amount bigger and more powerful and obviously faster. ac 72 will go up to 70 knots. >> there has been a lot of secrecy of the design and construction of the boats. has the technology changed a lot in the last few years? >> yeah. the concept of the boats have changed. we used to sail single haul boats with a keel attached to the bottom of them to keep the boat upright. catamarans, two hauls, wide platform, no keel, very light boats with a lot of sail area.